Lignocellulosic biomass residues, such as corn stover and wheat straw, typically contain about 30-45 wt % cellulose, 15-30 wt % hemicellulose, and 10-25 wt % lignin (Huber et al., “Synthesis of Transportation Fuels from Biomass: Chemistry, Catalysts, and Engineering,” Chemical Reviews 106:4044-4098 (2006)). These low value materials (deliverable at about $50/dry ton) (EPA Combined Heat and Power Partnership: Biomass CHP Catalog 14, Sep. 18, 2013) are currently underutilized, and could be converted to higher value bio-based products and biofuels through various pathways (Huber et al., “Synthesis of Transportation Fuels from Biomass: Chemistry, Catalysts, and Engineering,” Chemical Reviews 106:4044-4098 (2006); Brown et al., “A Review of Cellulosic Biofuel Commercial-Scale Projects in the United States,” Biofuels, Bioprod. Biorefin. 7:235-245 (2013)).
The production of advanced “drop in” hydrocarbon fuels has received intense interest (Brown et al., “A Review of Cellulosic Biofuel Commercial-Scale Projects in the United States,” Biofuels, Bioprod. Biorefin. 7:235-245 (2013)). The primary motivation of the biofuel industry includes a vast market capacity ($99 billion in 2014) (PRNewswire http://www.prnewswire.com/(2014)), minimizing the dependence on foreign petroleum, decreasing greenhouse emissions, and creating jobs. Existing technologies for the production of “drop in” biofuels include fermentation, pyrolysis, gasification, and liquid phase refinery approaches. However, the main problem with these existing technologies is that the production costs of advanced “drop in” fuels is too high to compete with conventional fuels. Novel technologies that can address economic and environmental problems are highly demanded.
Levulinic acid, or 4-oxopentanoic acid, can be produced in high yield through acid-catalyzed dehydration and hydrolysis of hexose sugars. Levulinic acid has also been identified by the U.S. Department of Energy as one of the “top 10” platform molecules derived from cellulosic biomass. The production of levulinic acid from carbohydrates in the presence of mineral acids has been practiced in a long history since Dutch professor G. J. Mulder first discovered this process in the 1840's. When treated at 140-210° C. for several hours in the presence of 1-5 wt % sulfuric acid (Rackemann et al., “The Conversion of Lignocellulosics to Levulinic Acid,” Biofuels, Bioprod. Biorefin. 5:198-214 (2011)), cellulose first depolymerizes into 5-hydroxymethylfurfural (HMF), followed by hydration and decomposition to form levulinic acid and formic acid in approximately equal molar amounts. Excellent yield (70-80% of the theoretical yield) could be obtained from various biomass feedstocks, such as corn stover, wheat straw, pine saw dust, etc. Meanwhile, furfural can also be obtained from the conversion of hemicellulose with ˜70% yield in this process. Furfural can be sold as a higher-value byproduct at a market price of ˜$1,000/dry ton. Some amount of humin (carbonaceous solids) could be generated as the byproduct. Biofine Inc. has proposed that humin can be utilized as valuable fuel to provide heat for an entire facility. The production cost of levulinic acid has been estimated to be ˜$0.04-$0.1 per pound if produced at a sufficiently large scale (˜1,000 dry ton/day).
The aqueous broth obtained from the above-mentioned acid-treating process typically contains 5 wt % levulinic acid and 2 wt % formic acid. Traditional methods developed by Biofine Inc. utilize lime to neutralize sulfuric acid, followed by distillation to separate water, formic acid, and levulinic acid. This process consumes lime and sulfuric acid and produces gypsum (calcium sulfate) as a low-value by-product. Thus, it is neither energy efficient nor environmentally friendly (Kamm et al., Biorefineries—Industrial Processes and Products in Ullmann's Encyclopedia of Industrial Chemistry, 659-688 (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim (2006)).
Hence, other energy-saving approaches for the separation of levulinic acid and formic acid from aqueous solution have been explored. The most promising method is extraction. Suitable solvents for this purpose include chloroform, ethers, alcohols, esters, ketones, hydrocarbons, and ternary amines.
Hydrogen is very important in the conversion of biomass to hydrocarbons because biomass usually contains highly oxygenated compounds that require a further hydrotreating process to remove excessive oxygen content. However, the production of hydrogen requires an additional facility that could increase capital and operation costs at a significant level. Thus, co-production of hydrogen along with hydrocarbons is of importance to reduce production cost in a biorefinery. However, there are no known techniques that could produce hydrocarbons and hydrogen together from levulinic acid and its derivatives, particularly in one process.
There are several existing technologies for the production of solely hydrocarbons from levulinic acid that generally employ multiple processing steps. For instance, Dumesic developed a three-step process to convert levulinic acid to C8+ olefins (Bond et al., “Integrated Catalytic Conversion of γ-Valerolactone to Liquid Alkenes for Transportation Fuels,” Science 327:1110-1114 (2010); Bond et al., “Production of Renewable Jet Fuel Range Alkanes and Commodity Chemicals from Integrated Catalytic Processing of Biomass,” Energy Environ. Sci. 7:1500-1523 (2014); PCT Publication No. WO/2008/151178). First, gamma-valerolactone (“GVL”) was obtained from the hydrogenation of levulinic acid using RuSn catalyst. Second, gamma-valorolactone was passed through a silica-alumina catalyst to produce butenes after decarboxylation. Third, C8, C12, and C16 olefins were produced through oligomerization of butenes using HZSM-5 or Amberlyst-70 solid acid catalyst. The total yields of C8-C16 olefins are approximately 50-60%. This process does not need additional hydrogen, but uses a noble metal (Ru) catalyst and employs three steps. The same group also developed a process to convert gamma-valerolactone to 5-nonanone via hydrogenation, decarboxylation, and coupling reactions using Pd/Nb2O5 catalyst. The total yield of 5-nonanone is approximately 60%. However, 5-nonanone has to be further upgraded through a hydrodeoxygenation reaction to obtain hydrocarbons which are suitable to be used as diesel and gasoline. The main drawback of this process is that an additional hydrogen production facility is required, and so is the use of a noble metal catalyst.
Another approach developed by Mascal can produce C7-C10 hydrocarbons (primarily gasoline components) from levulinic acid (Mascal et al., “Hydrodeoxygenation of the Angelica Lactone Dimer, a Cellulose-Based Feedstock: Simple, High-Yield Synthesis of Branched C-7-C-10 Gasoline-like Hydrocarbons,” Angew Chem. Int. Ed. Engl. 53:1854-1857 (2014)). The total yield is approximately 73%. But the process includes three steps (dehydration, coupling reaction, and hydrogenation). This process also requires the construction of an additional hydrogen supply facility that may increase capital costs by 50%.
Another process employs thermal treatment to convert dry calcium levulinate to produce a mixture of hydrocarbons and ketones in one pass (Schwartz et al., “Energy Densification of Levulinic Acid by Thermal Deoxygenation,” Green Chem. 12:1353 (2010)). However, the yield of this process is not reported, and an additional neutralization step to convert levulinic acid to calcium levulinate with lime is required. The main drawback of this process is that water has to be removed from levulinic acid feedstock, and there is a high energy input demand owing to a high reaction temperature (450° C.).
Another approach can produce GVL, pentanoic acid, butenes/butanes from the total deoxygenation of levulinic acid in the presence of trifluoromethylsulfonic acid and 316 stainless steel powder catalyst (Elham et al., “Stainless Steel As a Catalyst for the Total Deoxygenation of Glycerol and Levulinic Acid in Aqueous Acidic Medium,” ACS Catalysis 1.355 (2011)). They proposed that 316 stainless steel could act as the catalyst for this process. However, they did not report the production of higher hydrocarbons (>4 carbon atoms) that are suitable for use as transportation fuels.
Another approach can produce linear C9 ketones (nonane) through ketonization of levulinic acid with alkaline red mud catalyst. According to this approach it was proposed that linear chain hydrocarbons could be obtained with further hydrogenation of linear C9 ketones. As such, in the presence of red mud catalyst (primarily composed of iron, titanium dioxide, alumina, silica), external hydrogen supply at significantly high temperatures (365° C.), an organic phase being primarily composed of the desired linear C9 total deoxygenation products of the reaction cascade starting with LA ketonization along with some of the corresponding alcohols was obtained by the hydrogenation of C9 ketone derived from the upgrading of levulinic acid. They did not report the presence of cycloalkenes and hydrogen. When no catalyst and no hydrogen was applied, the yield of organic phase product was rather low (<10%) (Elham et al., “Ketonization and Deoxygenation of Alkanoic Acids and Conversion of Levulinic Acid to Hydrocarbons Using a Red Mud Bauxite Mining Waste as the Catalyst,” Catalysis Today 190:73-88 (2012)). The main drawback of this process is a high reaction temperature and no production of hydrogen.
The present invention is directed to overcoming these and other deficiencies in the art.